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What is the difference between an infection and a disease?
Infection, often the first step, occurs when bacteria, viruses or other microbes that cause disease enter your body and begin to multiply.
For instance, a person gets the disease malaria if he/she carries an infection caused in his/her body by the bit of the female Anopheles mosquito.

What is the difference?
COMMUNICABLE
A disease that can be passed from one person to another person, animal, or object.
NON-COMMUNICABLE
Diseases that are not transmitted from one person to another.
Sometimes called infectious or contagious diseases.

Communicable diseases are caused by several kinds of tiny life forms.
These microorganisms that cause diseases are called pathogens .
Sometimes you will hear pathogens called “germs”.
They are specialized to infect body tissues where they reproduce and cause damage that gives rise to the symptoms of the infection.
An infection is a condition that occurs when pathogens enter the body, multiply, and damage cells.

The two most common kinds of pathogens are:
• bacteria
• viruses
Others include:
• fungi
• parasites
• prions
Let’s look at each type in more detail.

They are possibly the most numerous types of organisms on the planet.
Some bacteria are harmful, but most are harmless or even helpful.
Bacteria were the first organisms to appear on earth, about 4 billion years ago. Our oldest known fossils are of bacteria-like organisms.
Streptococcus bacteria
Escheria coli
(e. coli) bacterium

Caused by Bacteria o Streptococcus pyogenes – (AKA strep throat) The throat gets irritated and inflamed, causing a sudden, severe sore throat o Pneumonia - lung inflammation caused by bacterial or viral infection, in which the air sacs fill with pus and may become solid o Meningitis - an infection of the membranes covering the brain and/or spinal cord o Salmonella – bacterium that occurs mainly in the intestine, especially a serotype causing food poisoning o Whooping cough - most affecting children, characterized by convulsive coughs followed by a whoop

Some of the most deadly diseases and devastating epidemics in human history have been caused by bacteria.
In the year 1900 pneumonia, tuberculosis and diarrhea were the three biggest killers in the USA.
As water purification improved, vaccines and immunization programs evolved, and antibiotic treatment became more advanced - the human death toll in the USA from bacterial diseases has dropped significantly (as well as in the rest of the developed world).
In developing countries, success rates have depended on several factors, such as the strategies implemented by local health authorities, and whether countries enjoyed periods of peacetime (no wars).

Strep Throat
Plague – aka “Black Death”
Typhoid fever

Viruses are the smallest disease-causing organism. They are even smaller than a bacteria.
They depend upon a host to survive, grow and reproduce. They can’t live outside of other living cells.
The host is who/what they live in or on.
Once they are inside the body, viruses can spread and make people sick. They reproduce by injecting their genes into a cell to produce thousands of new viruses.
Different viruses attack specific cells – so the flu virus attacks the cells of the respiratory system while the virus which causes meningitis attacks the cells of the membranes which cover your brain.

Caused by Viruses o common cold causes inflammation in the mucous membranes lining the nose and throat.
o influenza -the flu a viral infection of the respiratory tract.
o chicken pox o cold sores o Hand-Foot-and-Mouth Disease - viral illness that usually affects infants and children younger than 5 years old. Symptoms include fever, blister-like sores in the mouth and a skin rash.

Chicken pox
Shingles
Mononucleosis
Cold sore
Warts
Hand-Foot-and-Mouth Disease

Fungal diseases are often caused by fungi that are common in the environment.
Most fungi are not dangerous, but some types can be harmful to health.
There are approximately 1.5 million different species of fungi on Earth, but only about
300 of those are known to make people sick.
Some fungal diseases may be more common than previously realized, and rare but newly-emerging fungi are becoming increasingly problematic.
Antibiotic penicillin is made from the fungus Penicillium notatum.
Brewers' and bakers' yeast are types of fungi that grow as individual cells. They have been used for many centuries in the production of beer, wine and bread.
Diseases such as athlete's foot, ringworm, oral and vaginal thrush are examples of fungal infections.

ringworm
Thrush caused by candida yeast
Athletes foot

A parasite is an organism that lives on or in a host organism and gets its food from or at the expense of its host (who/what it is in or on) .
Parasites can cause anything from mild disease to death to the host. Parasites can also spread diseases from one organism to another.
Protozoa are one-celled organisms that can be free-living or parasitic in nature.
Malaria is a disease caused by a protozoa that live in certain kinds of mosquitoes. If an affected mosquito bites a human, the person will be infected. Out of all the parasitic diseases, malaria causes the most deaths globally. It kills approximately 627,000 people each year.
People living in the poorest countries are the most vulnerable to malaria. In 2012, 90% of all malaria deaths occurred in the WHO African Region, mostly among children under 5 years of age.
Parasitic organisms which affect the health of people include fleas and head lice which live on the outside of the body and tapeworms which live inside the body.

Elephantiasis is the result of a parasitic infection caused by three specific kinds of round worms.
Guinea worm disease
Rocky Mountain Spotted Fever
Lyme Disease is caused by a bacteria carried primarily by deer ticks

During the past two decades, evidence has linked some degenerative disorders of the central nervous system to infectious particles that consist only of protein. All known prion diseases frequently result in brain tissue that is riddled with holes.
The known prion diseases include Creutzfeldt-Jakob disease (in humans), scrapie (in sheep), and bovine spongiform encephalopathy ("mad cow disease" in cattle).
While some prion diseases are inherited, others are apparently due to infection by eating infected tissue or inadvertently through medical procedures such as tissue transplants.

When pathogens enter in to your body you get sick.
Pathogens enter the body in the following ways:
 Airborne or droplet infection (colds, flu).
 Animal borne or insect borne infection (rabies, malaria, Lyme Disease).
 Blood borne infection (HIV, hepatitis).
 Food borne or water borne infection (salmonella, giardia).
 Sexually transmitted (chlamydia, gonorrhea, syphilis).
 Other direct contact (some kinds of warts, scabies).
 Indirect contact (colds and flu carried from person to person on dirty tissues, money, door knobs, phones, computer keyboards).

1.
Good hygiene – wash hands often
2.
Clean utensils before using
3.
Cough & sneeze into your sleeve
4.
Avoid touching your eyes, nose, and mouth. Especially when sick.
5.
Do NOT share personal items – water bottles, toothbrushes etc.
6.
Use insect repellent
7.
Stay home when sick
8.
Clean and disinfect commonly used surfaces
9.
Get vaccinated
10.
Avoid touching wild animals

Eyes, Skin, Stomach, Saliva and Mucus
2. Immune System a. Nonspecific Response – inflammation and increased blood flow b. Specific Response – targets the pathogen in a specialized way
3. Lymphatic System – carries fluid known as lymph and produces white blood cells known as lymphocytes.
There are 2 kinds of lymphocytes:
B-cells
2. T-cells

B-Cell
• Formed in the bone marrow
• Release antibodies
• Produce specific antibodies
• These antibodies remain in the body
T-Cells
• Produced in the thymus gland
• Attack pathogens directly
• Killer T-cells attack directly
• Helper T-cells activate B-cells

Natural Immunity:
- present at birth
- includes the skin, mucus, and white blood cells
Acquired Immunity
- develops over time
- includes passive and specific immunity
- Passive Immunity is when mom passes antibodies to her child.
- Active Immunity is when you body makes specific antibodies for a pathogen
Vaccines
- dead or weakened pathogens
- will not cause illness
- triggers body to make antibodies